User's Manual

126 UltraWAVE Micro BTS Installation and Commissioning Guide, Version B
Chapter 5 - On-Line Commissioning
5.3.3 Voltage Standing Wave Ratio (VSWR) Check
The antenna and feeder cable VSWR measurement should be performed before
the Micro BTS installation and commissioning by the team responsible for the
antenna installation using a VSWR meter. The required VSWR is 1.5 or less. It is
very important to confirm the antenna and feeder installation to ensure the Micro
BTS transmits its signal power to the air effectively.
The purpose of this check is to ensure the integrity of the antenna and the
antenna connection under the actual full power condition by determining whether
the reflected power reading is lower than the required value. The reflected power is
derived from the antenna and feeder VSWR. Table 5-5 shows the direct
relationship between VSWR and reflected power.
The recommended test approach is to use an in-line, forward/reflected power
meter (for example, Thruline Watt Meter by Bird Electronics or the NAS model by
Rohde and Scorers) inserted between the Micro BTS chassis and the antenna
cable. This approach validates that the antenna and cable are good. It also verifies
that the transmit power from the chassis is within tolerance limits. Record the
reflected power which should be less than 4% of the output power as measured in
Step 10.
If the measured reflected power is more than 4% of the forward power, it indicates
power installation of the antenna or a bad feeder cable. Contact the responsible
party for the antenna and feeder cable installation to have the problem fixed.
Table 5-5: VSWR and Reflected Power
VSWR Reflected Power (% of the Output Power)
1.2 0.8%
1.3 1.7%
1.4 2.8%
1.5 4.0%
1.6 5.3%
1.7 6.7%
2.0 11.1%
3.0 25.0%
4.0 36.0%